Kitchen exhaust recovery system

ABSTRACT

Example embodiments of the described technology provide an exhaust hood for removing effluent plumes produced by cooking activity. The exhaust hood may comprise an exhaust fan operable to create a region of negative pressure beneath the exhaust hood for drawing air entraining the effluent plumes into the exhaust hood. The exhaust hood may also comprise one or more plenum chambers in fluid communication with the exhaust fan. The exhaust hood may also comprise one or more orifices in fluid communication with the one or more plenum chambers, the orifices located along a front edge of the exhaust hood. The exhaust hood may also comprise a filter for cleaning the air drawn into the exhaust hood such that air entraining the effluent plumes drawn into the exhaust hood by the exhaust fan is drawn through the filter to yield cleaned air. The exhaust hood may deliver at least a portion of the cleaned air into the one or more plenum chambers. The orifices may be configured to eject the portion of the cleaned air as one or more jets arranged to provide an air curtain.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from U.S. application No. 63/041705 filed 19 Jun. 2020 and entitled KITCHEN EXHAUST RECOVERY SYSTEM which is hereby incorporated herein by reference for all purposes. For purposes of the United States of America, this application claims the benefit under 35 U.S.C. § 119 of U.S. application No. 63/041705 filed 19 Jun. 2020 and entitled KITCHEN EXHAUST RECOVERY SYSTEM.

TECHNICAL FIELD

This invention pertains to ventilation systems. Particular embodiments of the invention relate to residential kitchen exhaust recovery systems.

BACKGROUND

Many residential kitchens have ventilation systems which provide routes for exchange, ventilation, circulation and/or movement of gas produced through cooking. Ventilation systems provided above a stove or cooktop in the kitchen are often referred to as range hoods or exhaust hoods. Exhaust hoods typically comprise an exhaust fan which draws air containing compounds released by cooking into one or more vents. The exhaust fan creates an area of reduced pressure to draw cooking gases into the vents. The vented air may contain contaminants such as grease, steam, vapors, fumes, smoke, steam, heat, odours and particulate matter.

Exhaust hoods may be configured to provide a fluid pathway for facilitating travel of cooking effluent drawn into the vents into a duct system of the building, which eventually expels the cooking effluent into the external atmosphere. This is referred to as a ducted exhaust hood. In contrast, a ductless exhaust hood recirculates cleaned or filtered cooking effluent back into the kitchen environment after passing the cooking effluent through a filter.

Conventional residential exhaust hoods are limited in their ability to capture and contain cooking effluent. One reason for this is that due to space and design considerations many residential exhaust hoods do not extend far enough out from a wall to completely cover a stove or cooktop. Also, many residential exhaust hoods have flat bottoms which allow cooking effluent which is not immediately captured upon reaching the vents to diffuse into the surrounding environment within the kitchen.

The capture efficiency of an exhaust hood is defined as the ratio of cooking effluent brought into the exhaust hood for processing versus the total amount of cooking effluent produced.

It is typically desired that an exhaust hood for residential use should fit within a small envelope. This limitation may arise from an aesthetic desire to not have the exhaust hood protrude further from the kitchen wall than surrounding furniture. However, this often results in a segment of a cooktop that extends farther than the exhaust hood and which therefore remains uncovered. Accordingly, cooking effluent produced in that the uncovered segment of the cooktop may not be effectively drawn into the exhaust hood. Exhaust plumes tend to rise upwards and will escape if they are not drawn strongly enough toward the exhaust hood. This issue may be partially mitigated by providing a higher capacity exhaust fan. However, an exhaust fan operating at high capacity can be undesirably loud and may deter use of kitchen exhaust systems altogether.

In some segments of the residential construction market there is a strong desire for compact, visually attractive exhaust hoods that meet specifications for energy efficiency and yet are inexpensive. There is a need for exhaust hoods that are viable in such cost conscious market segments and yet perform well for treating cooking effluent.

There is therefore a general need for cost effective kitchen exhaust systems which are able to obtain a high capture efficiency while having a small envelope. There is also a general desire for exhaust hoods that are quiet in operation.

The foregoing examples of the related art and limitations related thereto are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings.

SUMMARY

The following embodiments and aspects thereof are described and illustrated in conjunction with systems, tools and methods which are meant to be exemplary and illustrative, not limiting in scope. In various embodiments, one or more of the above-described problems have been reduced or eliminated, while other embodiments are directed to other improvements.

This invention has a number of aspects. These aspects have synergies when combined but may also be applied individually or in any combination. These aspects include, without limitation:

-   -   systems for removing effluent plumes produced by cooking         activity;     -   systems for filtering air entraining effluent plumes, the         filtered air appropriate for recirculating in a kitchen         environment;     -   systems for creating regions of negative pressure around exhaust         hood assemblies through the generation of air curtains;     -   systems for controllably pressurizing air within exhaust hood         assemblies such that air jets exit from orifices at desired         velocities and flow rates; and     -   systems and methods for providing automatic control of exhaust         hood assemblies based on sensed signals.

One aspect of the invention provides an exhaust hood for removing effluent plumes produced by cooking activity. The exhaust hood may include an exhaust fan operable to create a region of negative pressure beneath the exhaust hood for drawing air entraining the effluent plumes into the exhaust hood. The exhaust hood may include one or more plenum chambers in fluid communication with the exhaust fan. The exhaust hood may include one or more first orifices located along a front edge of the exhaust hood, the first orifices in fluid communication with the one or more plenum chambers. The exhaust hood may include a filter for cleaning the air entraining the effluent plumes drawn the exhaust hood to yield cleaned air. A portion of the cleaned air may be delivered into the one or more plenum chambers while another portion of the cleaned air is ejected from the first orifices as one or more jets to provide a first air curtain.

In some embodiments, the exhaust hood includes one or more second orifices in fluid communication with the one or more plenum chambers, the second orifices configured to eject air in a rearward direction as one or more second jets. The second jets may be generally horizontal. In some embodiments, the exhaust hood includes one or more third orifices in fluid communication with the one or more plenum chambers, the third orifices configured to eject at least a portion of the cleaned air in a downward direction as one or more third jets to provide at least one air curtain extending along at least one side of the exhaust hood. The exhaust hood may include one or more baffles disposed in the plenum chambers for adjustably varying a distribution of the cleaned air between the first and third orifices.

In some embodiments, the exhaust hood is configured to be mounted over a cooktop comprising an area which extends past a front portion of the exhaust hood. In some embodiments, the first jets are ejected at a forward angle relative to a vertical direction. In some embodiments, the exhaust hood includes a generally horizontal diffuser supported at a lower portion of the exhaust hood behind the first air curtain. The diffuser is configured to block upward motion of effluent plumes and to concentrate the region of negative pressure to a perimeter of the exhaust hood.

In some embodiments, a bottom rear portion of the exhaust hood is continuous with a wall to which the exhaust hood is configured to be mounted. In some embodiments, the overall length of the exhaust hood is smaller than an overall length of a cooking appliance over which the exhaust hood is configured to be mounted. In some embodiments, the exhaust hood includes a recess formed by panels that extend downwardly around a bottom perimeter of the exhaust hood.

In some embodiments, the exhaust hood includes an activated carbon filter. In some embodiments, the exhaust hood includes a second fan located downstream of the filter. The second fan may be operable to pressurize the one or more plenum chambers with the cleaned air. In some embodiments, the exhaust hood includes an intake fan operable to draw ambient air into the one or more plenum chambers. In some embodiments, the first orifices are positioned on a forward-facing surface of the exhaust hood.

In some embodiments, the exhaust hood includes a controller for providing automatic control of the exhaust hood. Automatic control of the exhaust hood may be based on signals sensed from one or more of a heat sensor, an appliance state sensor, and a particulate matter sensor. Automatic control of the exhaust hood may involve controlling one or more of: the size of openings for diverting cleaned air into the plenum chambers, the angle of one or more baffles disposed between the plenum chambers and any of the orifices, an angle of the first jets, and a suction power of the exhaust fan.

Another example aspect of the invention provides an exhaust hood for capturing effluent plumes produced at a cooktop. The exhaust hood comprises a body mountable against a wall, the body having a rear side for abutting the wall and a front side spaced from the rear side, the body having vents formed on a lower surface thereof. A fan is located within the body and toward the rear side of the body. The fan is connected to draw air and any entrained cooking effluent through the vents into an interior space of the exhaust hood and to deliver at least some of the air through a filter and into a plenum located within the exhaust hood. First apertures are arranged along the front side of the body. The apertures are fluidly coupled to the plenum and arranged to provide a first air curtain that extends across the front side of the body and is directed forward and downward from the exhaust hood.

In some embodiments the front and rear surfaces of the body are spaced apart by a distance of about 12 inches (e.g. 10 to 14 inches or 11 to 13 inches.

In some embodiments the exhaust hood includes second apertures arranged to extend along one or two lateral sides of the exhaust hood between the front and rear sides of the body, the second apertures fluidly coupled to receive filtered pressurized air within the body to provide a second air curtain that extends along one or both of the lateral sides of the body and is directed downwardly from the exhaust hood.

In addition to the exemplary aspects and embodiments described above, further aspects and embodiments will become apparent by reference to the drawings and by study of the following detailed descriptions.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments are illustrated in referenced figures of the drawings. It is intended that the embodiments and figures disclosed herein are to be considered illustrative rather than restrictive.

FIG. 1 is a schematic drawing of a kitchen exhaust hood configured to provide air curtains for drawing effluent plumes toward the exhaust hood according to an example embodiment of the invention.

FIG. 1A is a schematic illustration showing a geometry of an exhaust hood installation. FIG. 1B is a schematic cross section of an edge portion of an exhaust hood that supports orifices for forming an air curtain.

FIG. 2 is a perspective view of a portion of an exemplary exhaust hood showing the generation of air jets for generating air curtains.

FIG. 3 is a perspective cross-sectional view of a kitchen exhaust hood configured to provide air curtains for drawing effluent plumes into the exhaust hood according to an embodiment of the invention.

FIG. 4 is a low-angle perspective view of the kitchen exhaust hood of FIG. 3.

FIG. 5 is a perspective view of a kitchen exhaust hood according to an embodiment of the invention.

FIG. 6 is a perspective cross-sectional view of the kitchen exhaust hood of FIG. 5.

FIG. 7 is low-angle perspective view of the kitchen exhaust hood of FIG. 5.

FIG. 8 is a side elevation view of the kitchen exhaust hood of FIG. 5.

FIG. 9 is a detailed perspective view of the kitchen exhaust hood of FIG. 5.

FIG. 10 is a schematic view of a system comprising an exhaust hood that is operated by a controller based on sensed signals from a number of sensors.

FIG. 11A is a computational fluid dynamic (CFD) simulation of gas flow around an exhaust hood in the absence of generated air curtains.

FIG. 11B is a CFD simulation of gas flow around an exhaust hood when air curtains are generated.

FIG. 12A is a CFD simulation of gas flow around an exhaust hood when a vertical air curtain is generated.

FIG. 12B is a CFD simulation of gas flow around an exhaust hood when an angled air curtain is generated.

FIG. 13A is a simulation of steam flow around an exhaust hood when a vertical air curtain is generated.

FIG. 13B is a simulation of steam flow around an exhaust hood when an angled air curtain is generated.

DESCRIPTION

Throughout the following description specific details are set forth in order to provide a more thorough understanding to persons skilled in the art. However, well known elements may not have been shown or described in detail to avoid unnecessarily obscuring the disclosure. Accordingly, the description and drawings are to be regarded in an illustrative, rather than a restrictive, sense.

FIG. 1 is a schematic diagram illustrating an exhaust hood 10 according to an example embodiment. Cooking activity performed on cooktop 12 produces cooking effluent plumes 14 (represented by effluent plumes 14A, 14B and 14C). Discrete cooking effluent plumes 14A-14C are merely shown as an illustrative example. Each effluent plume 14 is shown to illustrate the behaviour of effluent produced by cooking activity performed in a corresponding region of cooktop 12. Cooking effluent may arise from any part of cooktop 12.

In FIG. 1, cooking effluent plumes 14A and 14B originate at locations which are directly below exhaust hood 10 and so tend to rise naturally toward a bottom surface of exhaust hood 10 where one or more vents 16 are located. Plumes 14A and 14B originate from cooking activity performed over region 12A of cooktop 12 which is covered by the vertical projection of exhaust hood 10 onto cooktop 12. Plume 14C originates from cooking activity performed over region 12B of cooktop 12. Region 12B is an area of cooktop 12 not covered by the vertical projection of exhaust hood 10. Exhaust fan assembly 18 is operable to create a region of relative negative pressure underneath fan 18 to draw cooking effluent through vents 16 into an interior space of exhaust hood 10.

Exhaust hood 10 is configured to provide an air curtain 20 by ejecting air downward and in a forward direction at an angle θ from locations at or near an edge 22 of exhaust hood 10. Angle θ is the angle formed between the direction of travel of air in air curtain 20 and a vertical axis. FIG. 1A schematically shows a geometry of exhaust hood 10 and air curtain 20. Cooktop 12 projects farther from rear wall 11 than exhaust hood 10 by a distance D. Accordingly, cooktop 12 can be considered to have a length that is greater than that of exhaust hood 10. Air curtain 20 is angled so that a circulating airflow 21 is established above cooktop 12. Any cooking effluent from cooktop 12 is caught up in airflow 21 and brought to vent(s) 16.

Angle θ may be chosen such that angled air curtain 20 just clears the outer edge 12B of cooktop 12. For example, where air curtain 20 originates at a height H above the top of cooktop 12 and cooktop 12 projects a distance farther from wall 11 than the origin of air curtain 20, the angle θ may be slightly larger than arcsin(D/H).

The angle θ at which air curtain 20 is discharged from exhaust hood 10 should be dependent on the dimensions of cooktop 12 and the position of edge 22 of exhaust hood 10 in relation to cooktop 12. If air curtain 20 is generated at an angle θ that is too steeply downward, air curtain 20 may reach effluent plume 14C at or close to the upper surface of cooktop 12 and therefore force effluent plume 14C away from vents 16 and into the surrounding kitchen environment, which is an undesirable outcome.

Angled air curtain 20 may be generated by expelling directed jets air from locations at or near edge 22 of exhaust hood 10. FIG. 2 illustrates one example construction for providing air curtain 20. Edge 22 comprises a plurality of orifices 24 through which air jets 26 are ejected. Air jets 26 collectively form air curtain 20. Although only a few air jets 26 are shown in FIG. 2, it will be understood that air jets 26 may be ejected from some or all of orifices 24.

In some embodiments (see e.g. FIG. 1), edge 22 is chamfered to provide a surface that is at least generally perpendicular to jets 26. Air exiting orifices 24 is travelling in the plane of air curtain 20 at angle θ to vertical.

In some embodiments the direction of air curtain 20 is defined by the orientation of nozzles that are oriented non-perpendicularly to a face of exhaust hood 10 from which jets 26 are directed. For example, in such embodiments, edge 22 may be co-planar with a front or bottom surface of exhaust hood 10. In such embodiments, a plurality of appropriately angled nozzles 24 can be provided to generate air curtain 20 at angle θ.

In FIG. 2, air jets 26 originate from orifices or nozzles 24 that are arranged in a linear configuration and so air curtain 20 is generally planar in configuration. This is not mandatory. In some embodiments orifices 24 are arranged to produce other configurations of air curtains. For example, orifices 24 may be arranged along an arc or curve. Such an arrangement of orifices 24 may, for example, provide an air curtain which is convex on its face away from wall 11. Differently shaped air curtains may exploit fluid dynamic effects to capture cooking effluent.

In some embodiments, the velocity of air exiting air curtain 20 is uniform along the length of edge 22. In other embodiments, the velocity of ejected air along the length of edge 22 varies. For example, the velocity of air ejected in a middle portion of edge 22 may be made to be greater than the velocity of air ejected at locations near the ends of edge 22.

In some embodiments, the velocity profile of air curtain 20 is automatically determined using appropriate sensors and/or is user configurable. For example, it may be desirable to limit or concentrate the ejection of air jets 26 to areas above where cooking activity is being performed. For example, a user control may allow the user to select among options such as providing air curtain 20 over the full width of exhaust hood 10, concentrating air curtain 20 toward the right-hand side of exhaust hood 10 or concentrating air curtain 20 toward the left-hand side of exhaust hood 10.

In some embodiments the temperature and/or humidity of air being drawn into vent(s) 16 is monitored by one or more sensors in exhaust hood 10 to obtain a measure of the amount of cooking effluent being generated. In some such embodiments a velocity and/or volume of air in air curtain 20 is automatically adjusted based on the measure of the amount of cooking effluent (e.g. the velocity and/or volume of air in air curtain 20 may be increased as the measure of the amount of cooking effluent increases).

The term “Bernoulli principle” describes the reduction in pressure that results near a region of fast flowing fluid. Because of the Bernoulli principle the fast-flowing air in air curtain 20 causes a reduced pressure that tends to entrain surrounding air. Exhaust hood 10 exploits this principle to carry effluent plume 14C toward vent 16 of exhaust hood 10. Preferably, air curtain 20 has a high velocity while occupying a low volume, effectively creating an area of low pressure around edge 22 which, at the same time, causes minimal disruption to air flowing in the path of air curtain 20. This may be achieved, for example, by keeping orifices 24 small in diameter. For example, orifices 24 may have diameters in the range of 2-10 mm, each orifice spaced from adjacent orifices at a distance of 1-5 cm. In this manner, exhaust hood 10 may advantageously capture a high volume of low velocity air, such as effluent plume 14C, arising from cooking activity performed over an uncovered portion 12B of cooktop 12 whilst permitting exhaust hood 10 to feature a smaller outward projection from wall 11 (i.e. a larger value of D). Furthermore, the size of orifices 24 and the distance separating each of them may differ depending on the relative position and configuration of exhaust hood 10 and cooktop 12.

Although FIG. 2 shows circular orifices 24, different shapes, configurations and numbers of orifices 24 are possible for ejecting air jets 26 of air curtain 20. For example, some embodiments provide for a single or multiple elongate orifices 24. In an example embodiment, orifices 24 comprise a single elongated slit that extends substantially all along the length of edge 22.

Exhaust hood 10 may be shallow in its dimension between a rear surface of exhaust hood 10 that abuts a wall and a front face of exhaust hood 10. For example, exhaust hood 10 may have a depth equal to that of cabinets that are above exhaust hood 10. In some embodiments exhaust hood 10 has a depth of 15 inches or less (e.g. a depth in the range of 10 to 14 inches). In some embodiments exhaust hood 10 has a depth of 12 inches ±1.5 inches.

In an illustrative example configuration, the forward edge of exhaust hood 10 is 12 inches away from a wall 11 of the kitchen and the forward edge of a cooktop 12 is 24 inches away from wall 11, the top surface of cooktop 12 being 30 inches below vents 16 of exhaust hood 10. In such a configuration, air curtain 20 has an angle θ preferably between 10 and 40 degrees from vertical. According to a specific embodiment, air curtain 20 has an angle θ of 28 degrees ±½ degree or ±1 degree or ±2 degrees from vertical.

In the above illustrative example individual air jets 26 forming curtain 20 preferably have a velocity between 5-6 m/s. In some embodiments air jets 26 have a velocity in the range of 2-10 m/s. In some embodiments, angle θ is adjustable over a selected range (e.g. in a range of 0 degrees (i.e. air jets 26 having a downward vertical orientation) to 90 degrees (i.e. air jets 26 having a horizontal direction) or in a range of about 20 degrees or 25 degrees to about 30 or 35 degrees). This may be achieved in any number of ways, including adjusting an angle of flexible nozzles through which air jets 26 are ejected or by tilting a pivotable portion of exhaust hood 10 on which orifices 24 are disposed. The ability to configure the angle at which air curtain 20 is generated advantageously allows for exhaust hood 10 to be adapted for use with cooktops 12 having a variety of sizes and dimensions. In other embodiments, angle θ is not user-adjustable and is set during the manufacturing process to accommodate a number of common configurations of cooktops 12.

In some embodiments, a portion of effluent plumes 14 and ambient air from the kitchen environment which is drawn into exhaust fan assembly 18 is expelled from exhaust hood 10 and discharged from the kitchen environment through one or more ducts 28. Meanwhile, a portion of drawn effluent plumes 14 and ambient air is driven toward orifices or nozzles along certain edges of exhaust hood 10 for generating the air curtains described herein. This may be achieved in a number of suitable ways. For example, exhaust fan assembly 18 may comprise an air flow splitter which directs a first portion of the air drawn into vent 16 to be discharged from the kitchen and directs a second portion of the air drawn into vents 16 to be recirculated as air curtains by way of channels 30.

In some embodiments, a constriction in ducts 28 results in an interior space 19 of exhaust fan assembly 18 being pressurized such that a portion the air drawn into vents 16 is directed through one or more channels 30 and is recirculated into the kitchen environment as one or more air curtains.

In some embodiments, all of the air entering vents 16 of exhaust hood 10 is recirculated into the kitchen environment. In embodiments where air is recirculated into the kitchen environment, exhaust hood 10 preferably comprises one or more filters for capturing grease, odours and other pollutants entrained in effluent plumes 14. Examples of suitable filters are discussed below.

In some embodiments, each of channels 30 comprises a plenum chamber, wherein pressurized air contained within the plenum chamber is expelled as air jets for generating the various air curtains described herein. In some embodiments, an air intake fan 32 is optionally provided in exhaust hood 10. Intake fan 32 comprises a blower that draws ambient air from the kitchen environment into the plenum chamber of each of the channels 30 by way of one or more ambient air channels 30A. Intake fan 32 may serve to controllably pressurize the air within channels 30 such that air jets 26 exit from orifices 24 at a desired velocity and flow rate.

In some embodiments, air drawn into vent(s) 16 is expelled fully through ducts 28 without filtration. In such embodiments, ambient air drawn from fan 32 may supply all of the air required for the creation of air curtains 20, 40 and 50 (discussed below).

In some embodiments, exhaust hood 10 comprises a means for conditioning air before the air is ejected to provide air jets 26. For example, an air conditioning unit provided within exhaust hood 10 may subject air to a system of vapor-compression refrigeration to cool the air before it is ejected as air jets 26. The use of conditioned air can advantageously improve user comfort by removing heat present in air drawn from above cooktop 12 before directing the conditioned air toward a user through air curtain 20. In addition or in the alternative, exhaust hood 10 may comprise an air-to-air heat exchanger to exhaust stale air outdoors and to bring in incoming fresh air.

In the example FIG. 1 embodiment, exhaust hood 10 comprises a diffuser 34 positioned to redirect effluent plumes 14 within exhaust hood 10. Diffuser 34 comprises a bottom surface that is at least substantially impermeable to rising plumes 14. To prevent leakage and escape of effluent plumes 14 from exhaust hood 10, diffuser 34 concentrates the negative pressure produced by exhaust fan assembly 18 at locations around the perimeter of exhaust hood 10, the perimeter being where effluent leakage into the surrounding kitchen environment is normally most likely to occur.

In some embodiments, diffuser 34 comprises a permeable interior that is open to the cooking environment at the perimeter of diffuser 34. This permeable interior is in fluid communication with one or more openings of exhaust hood 10 (e.g. vents 16). Effluent plumes 14 rising to the perimeter of diffuser 34 may flow freely through the permeable interior of diffuser 34. Diffuser 34 may therefore serve as a conduit for conveying the negative pressure created by fan assembly 18 to draw plumes 14 into the interior of exhaust hood 10. According to a particular embodiment, the permeable interior of diffuser 34 comprises a filter for capturing grease, odours and other pollutants entrained in effluent plumes 14.

Optionally, exhaust hood 10 comprises downwardly extending panels 35 along the perimeter of exhaust hood 10 to form a recess 37 within the perimeter of panels 35. Recess 37 creates a buffer zone effective to contain transient movements of effluent plumes 14 as plumes 14 reach exhaust hood 10 and before plumes 14 are drawn into hood 10. Provision of such a recess 37 serves to further contain and prevent the spillage of effluent plumes 14. In some embodiments, parts of recess 37 are defined by walls of adjacent cabinets or pantries. For example, exhaust hood 10 may be interposed between two kitchen cabinets which extend farther downward than side edges of exhaust hood 10 such that the cabinet walls form a part of panels 35 which form recess 37.

An exhaust hood 10 may feature an exhaust fan 18 located near the back of the exhaust hood 10, proximate to wall 11, for facilitating connection to the ductwork or to the electrical systems of a building. Accordingly, low pressure regions generated by exhaust fan assembly 18 may be stronger in areas closer to wall 11 than in areas toward the front of hood 10. Exhaust hood 10 of the example FIG. 1 embodiment may optionally provide nozzles which provide an air curtain 40 comprising jets of air oriented generally horizontally and flowing in a rearward direction across a lower surface of exhaust hood 10 toward wall 11.

Generation of air curtain 40 has the effect of directing the flow of effluent plumes 14 toward the back of exhaust hood 10, where the negative pressure generated by a rearwardly located exhaust fan assembly 18 (as shown in FIG. 1) is at a maximum, thereby improving the capture efficiency of exhaust hood 10. Generation of air curtain 40 also has the added advantage of providing a flow of air along the bottom surface of diffuser 34 which prevents or reduces the deposition of oils and other pollutants on diffuser 34, thus reducing the need for frequent cleaning or replacement of diffuser 34.

Air curtain 40 is generated from the ejection of air jets 46 from one or more rearward facing orifices 44 (i.e. toward wall 11) located on edge 42 of exhaust hood 10. In the illustrated embodiment, edge 42 is depicted in dotted lines to represent its location within the area of recess 37, formed by panels 35.

Air curtain 40 may have increased effectiveness for directing the flow of effluent plumes 14 toward the back of exhaust hood 10 by exploiting the principle of turbulent jets wherein ambient fluids are mixed and entrained within a jet of turbulent fluid. A lower velocity of air curtain 40 may be desired in some embodiments. The lower velocity permits the cross-sectional area of the turbulent air curtain 40 at a certain distance away from orifices 44 to be larger compared to if air curtain 40 was generated at a higher velocity. This larger cross-sectional area is advantageous for entraining more effluent plumes 14. In some embodiments, orifices 44 comprise a larger cross-sectional area such that air curtain 40 occupies a larger volume for entraining plumes 14. Despite any desire for air curtain 40 to have a lower velocity, air curtain 40 should be generated at a sufficiently high velocity for moving entrained plumes 14 to the back of hood 10.

In some embodiments, pressurized air used to generate air curtain 40 is supplied from the same channels 30 used to supply air for generating air curtain 20. Channels 30 may, for example, terminate at a chamber common to orifices 24 and 44 or be in fluid communication with orifices 24 and 44 in any other appropriate manner. In some embodiments, one or more baffles may be provided in a distal portion of channels 30 prior to orifices 24 and 44. The one or more baffles may be employed to controllably influence the distribution of airflow exiting through orifices 24 and 44 such that air curtains 20 and 40 are each generated at a desired velocity and/or velocity profile. In other embodiments, exhaust hood 10 comprises one or more pressure regulator valves at a distal end of channels 30 for generating air curtains 20 and 40 at a desired velocity and/or velocity profile.

A portion of exhaust hood 10 adjacent to wall 11 and below the area of maximum negative pressure generated by exhaust fan assembly 18 may be referred to herein as exterior portion 38. An example exterior portion 38 is illustrated in FIG. 1 as the back surface of exhaust hood 10 that is below diffuser 34. Preferably, exterior portion 38 comprises a bottom interfacing edge that is generally continuous with wall 11. Such a design exploits the Coanda effect which describes the tendency of a jet of fluid to adhere to an adjacent surface. As illustrated by effluent plume 14A, the adjacent flat surfaces of wall 11 and the continuously flat portion 38 directs effluent plume 14A to the area of maximum negative pressure near the back of exhaust hood 10. Corners or discontinuities can create pockets of air where fluid may mix, forming vortical flow patterns which therefore result in turbulent flows. Generally, a laminar flow of effluent plumes 14 along wall 11 is preferred over the occurrence of transient vortices regularly observed in rising smoke, which has a higher likelihood of escaping from exhaust hood 10. In this sense, by providing a continuous boundary between exterior portion 38 and wall 11, laminar flow of effluent plumes 14 is encouraged which thereby increases capture efficiency.

In one example embodiment, exterior portion 38 comprises a thin continuous flat wall which minimizes discontinuities between wall 11 and portion 38. The bottom portion of this flat wall may further comprise a ramp to eliminate corners which cause mixing. In other embodiments, a portion 38 of exhaust hood 10 is omitted while a recessed canopy 37 is formed by the other sides of exhaust hood 10 through downwardly extending panels 35. This embodiment has the advantage of providing a recess 37 to contain transient movements of effluent plumes 14 while using the continuous wall 11 to exploit the Coanda effect to allow plumes 14 to adhere to wall 11 and to avoid discontinuities which cause turbulence.

In some embodiments, a portion of air flowing through channels 30 is directed to and ejected at openings located along side edges of exhaust hood 10, thereby creating areas of low pressure along the lower side edges of exhaust hood 10. As shown in FIG. 2, a lower portion of exhaust hood 10 additionally comprises a plurality of orifices 54 disposed along each of the lower side surfaces 52. Air jets 56 are ejected from orifices 54 for generating side air curtains 50. Air curtain 50 is preferably generated at a sufficiently high velocity to exploit the Bernoulli principle to guide effluent plumes 14 toward vent(s) 16. In this manner, similar to principle of operation of air curtain 20, leaking of effluent plumes 14 from the sides of exhaust hood 10 may be reduced or eliminated. Such a design may also advantageously enable exhaust hood 10 to have a smaller width than that of cooktop 12 in a direction parallel to wall 11.

In the embodiment illustrated in FIG. 2, air curtain 50 is generated in a downward vertical direction, although this is not necessary. In other embodiments, air curtain 50 is generated at a direction angled downward and away from exhaust hood 10. Pressurized air for the creation of air curtain 50 may be supplied from channels 30 in the manner described above in relation to air curtains 20 and 40.

In other embodiments, pressurized air from channel 30 is diverted into a separate plenum chamber for supplying air to create air jets 56. Provision of a plenum chamber separate from the channel supplying air for air jets 26 and 46 may be desirable because orifices 54 extend away from the front of exhaust hood 10 where orifices 24 and 44 are located. Accordingly, the shared use of channels 30 could result in orifices 54 most proximate to channels 30 (closer to the front of hood 10 in the illustrated embodiment) to produce a higher velocity jet 56 while rearward orifices 54 (toward wall 11) produce jets 56 of comparatively lower velocity. In some embodiments two separate plenum chambers are located on opposing sides of exhaust hood 10 wherein these plenum chambers terminate at a centre portion of each of edges 52.

In some embodiments, one or more baffles are provided within exhaust hood 10 around edges 52 to control the velocity at which air exits orifices 54. In some embodiments, the one or more baffles are configured to allow air to exit orifices 54 as jets 56 at a uniform velocity. In other embodiments, the one or more baffles are configured to create a non-uniform velocity profile of jets 56. This may be desirable for creating low pressure regions which are concentrated only around where cooking activity occurs to reduce the air supply needs of exhaust hood 10. In some embodiments, the angle of air curtain 50 is adjustable. This may be accomplished by providing flexible nozzles through which air jets 56 are ejected or by tilting a pivotable portion of exhaust hood 10 on which orifices 54 are disposed (e.g. edge 52). The ability to configure the angle at which air curtain 50 is generated advantageously allows for exhaust hood 10 to be adapted for cooktops 12 having a variety of sizes.

Similarly, one or more baffles may be provided within exhaust hood 10 around edges 22 and 42. These one or more baffles may be configured to control the velocity at which air exits orifices 24 and 44 to achieve a desired velocity profile of air jets 26 and 46. This may be desirable in cases where channels 30 terminate at a centre of edges 22 and 42 such that the velocity of air exiting from orifices 24 and 44 situated on the sides would be comparatively lower than the air exiting from orifices near the middle, for example.

In some embodiments, exhaust fan assembly 18 has a capacity in the range of 100-300 cubic feet of air per minute (CFM). This range may be appropriate, for example, in residential, non-commercial kitchens. In some applications such as in commercial kitchens or in laboratories, exhaust fan assembly 18 may have a higher CFM rating.

In some embodiments the proportion of cleaned air to be recirculated as air curtains 20, 40 and/or 50 is in the range of 5-25% of the total air intake of exhaust hood 10.According to a specific embodiment, 11% of the total air intake of exhaust hood 10 is ejected as air curtains 20, 40 and/or 50. The remaining air drawn into exhaust hood 10 may be discharged from the kitchen environment through one or more ducts 28 or be otherwise recirculated into the kitchen environment.

FIG. 3 is a perspective cross-sectional diagram illustrating a ductless exhaust hood 100 according to an example embodiment. Exhaust hood 100 comprises an outer housing 110. Outer housing 110 may be supported over a corresponding cooktop in any appropriate manner. Outer housing 110 may further comprise any appropriate interfaces for connecting powered components within hood 100 to a power source. Diffuser assembly 112 is attached to and is supported by housing 110 in a bottom portion of exhaust hood 100 exposed to rising cooking effluent plumes 14. Diffuser assembly 112 comprises a plaque diffuser 114 which redirects effluent plumes 14 to the perimeter of exhaust hood 100, a portion of which is illustrated by perimeter 115. That is, plumes 14 rising by the buoyancy effect are impeded from further upward motion by diffuser 114 whereby the plumes 14 may only travel along the bottom surface of diffuser 114 thereafter. A first exhaust fan 122 may be operated to generate a negative pressure (i.e. a pressure that is less than ambient atmospheric pressure) in the areas of exhaust hood 100 below fan 122. This negative pressure is concentrated at the perimeter 115 of exhaust hood 100 around diffuser 114 and draws effluent plumes 14 into the interior of exhaust hood 100.

In the embodiment illustrated in FIG. 3, diffuser assembly 112 comprises a tray 116 which comprises attachment features for attaching diffuser assembly 112 to housing 110. Tray 116 further comprises an opening 118 for facilitating fluid communication between the interior of exhaust hood 100 to the air of the kitchen environment and, most significantly, to effluent plumes 14. Diffuser assembly 112 further comprises a filter 120 disposed above diffuser 114 and below tray 116. Filter 120 and diffuser 114 may be attached to tray 116 by any appropriate means. For example, corresponding holes may be provided in each of diffuser 114, tray 116 and filter 120 through which a snap-fit connector or another suitable type of connector can pass to thereby couple diffuser 114, tray 116 and filter 120. It is desirable that diffuser 114, tray 116 and filter 120 are removably coupleable to one another so that filter 120 can be accessed during the lifecycle of exhaust hood 100 for service or replacement.

Any appropriate filter for capturing grease, odours and other pollutants entrained in effluent plumes 14 may be used for filter 120. In the illustrated embodiment, filter 120 is a mesh-type filter and may be made from a variety of appropriate materials such as aluminum, charcoal, galvanized steel and stainless steel. Filter 120 of diffuser assembly 112 serves to condense water vapour in plumes 14 as well as to cool the air of plumes 14. Generally, hot air entrained with water vapour is less conducive to filtration than cool dry air. Passage of captured air through filter 120 therefore prepares the air for further and more efficient filtration within exhaust hood 110.

A lower separator panel 124 comprises an opening 126 allowing air to be drawn into and through a first exhaust fan 122 alongside ambient air within the kitchen environment. Solid arrows shown in FIG. 3 illustrate the direction of travel of air within exhaust hood 100. Fan 122 is mounted on a fan tray 128, fan tray 128 being supported within exhaust hood 100 by housing 110 and separator panel 124.

Exhaust hood 100 comprises a second exhaust fan 130 which may be operated to generate a negative pressure in an intermediate area 129 within exhaust hood 100 downstream of first exhaust fan 122 and upstream of second exhaust fan 130. Exhaust hood 100 comprises an activated carbon filter tube 132 located within intermediate area 129 for further cleaning of air 14, resulting in cleaned air 14D.

In the illustrated embodiment, fan 130 and filter tube 132 are attached to and supported within exhaust fan 100 by an upper separator panel 134, upper separator panel 134 in turn is supported by fan tray 128 and housing 110. A space 136 is defined by combined surfaces of housing 110, fan tray 128, and separator panels 124 and 134. Space 136 separates air downstream of filter tube 132 to thereby prevent mixing of cleaned air 14D with any upstream unfiltered air flow.

Fan 130 is operable to draw cleaned air 14D from space 136 into a terminal area 138 of exhaust hood 100. Exhaust hood 100 comprises an upper separator panel 140 for separating terminal area 138 from any unfiltered air flow upstream of filter tube 132.

As cleaned air 14D is drawn into and pressurized within terminal area 138, cleaned air 14D enters side plenums 142A and 142B (collectively referred to herein as side plenums 142) through openings 144A and 144B located on opposing side walls of housing 110 (collectively referred to herein as openings 144). As best shown in FIG. 4, showing a low-angle perspective view of exhaust hood 100, cleaned air 14D travels through side plenums 142 and enters a lower plenum 146. Similar to that which is illustrated in FIG. 2, lower plenum 146 comprises a forward-facing angled edge 154. Edge 154 comprises a plurality of orifices 156 through which pressurized clean air 14D is ejected. Through the combined ejection of air 14D from the plurality of orifices 156 which forms an air curtain, a low pressure region surrounding edge 154 is created to guide effluent plumes 14 toward exhaust hood 100 for capture and filtration This principle is described in detail above in relation to air curtain 20.

Lower plenum 146 additionally comprises a rearward facing surface 158 which comprises a plurality of orifices 160 through which pressurized clean air 14D is ejected. As described above in relation to air curtain 40, air 14D ejected from orifices 160 encourages efficient airflow across diffuser assembly 112. Air 14D ejected from orifices 160 additionally redirects plumes 14 to the back of exhaust hood 100 where there may be a higher negative pressure region to facilitate drawing plumes 14 into exhaust hood 100.

FIG. 5 is a perspective view of a ductless exhaust hood 200 according to an example embodiment. FIG. 6 is a perspective cross-sectional view of exhaust hood 200. Exhaust hood 200 comprises an outer housing 210 which may be supported over a corresponding cooktop in any appropriate manner. Exhaust hood 200 comprises a first filter 214 that is mounted to hood 200 by way of tray 216. Filter 214 may be a wire mesh filter that serves to capture grease, odours and other pollutants entrained in effluent plumes 14. Filter 214 may further serve to condense water vapour in plumes 14 as well as to cool the air of plumes 14. In some embodiments, filter 214 is a bonded aluminum mesh filter.

Exhaust hood 200 comprises a second filter 218 mounted overtop of filter 214 to housing 210 by way of tray 220. In the illustrated embodiment, second filter 218 comprises a bottom layer 218A and an upper layer 218B for further cleaning effluent plumes 14 passing therethrough, resulting in cleaned air 14D. In some embodiments, bottom layer 218A comprises a wool filter and upper layer 2186 comprises an activated carbon filter. The illustrated configuration has the advantage of capturing condensed droplets and oil mist accumulation using the wool filter. The cooled, air, which has a reduced moisture content enables the activated carbon filter to most effectively absorb any volatile organic compounds entrained in plumes 14.

First and second exhaust fans 222A and 222B may be operated to generate a negative pressure in the areas of exhaust hood 200 below fans 222A and 222B. Filters 214 and 218 are permeable such that they provide a conduit for conveying negative pressure created by fan 222A and 222B to draw effluent plumes 14 into the interior of exhaust hood 200. Fans 222A and 222B may be mounted to housing 210 of hood 200 by way of tray 224. Fans 222A and 222B are mounted in a co-planar configuration in the FIG. 6 configuration, although this is not necessary. In other embodiments, only a single exhaust fan 222 is utilized.

A portion of cleaned air 14D may pass through a third filter 228. In the illustrated embodiment, third filter 228 comprises bottom and upper layers 228A and 228B. For example, bottom layer 228A may comprise an activated carbon filter while upper layer 228B may comprise a wool filter. Third filter 228 is mounted to housing body 210 by way of tray 230. Exhaust hood 200 additionally comprises acoustic insulators 226A, 226B and 226C (collectively referred to herein as acoustic insulators 226) for attenuating sound waves produced through the operation of fans 222A and 222B. Acoustic insulators 226 may comprise any appropriate material for reducing the noise of exhaust hood 200 during operation, such as perforated metal sheets, wire mesh, and the like. In the illustrated embodiment, acoustic insulators 226A and 226C are mounted to tray 224 and housing 210. Acoustic insulator 226B is attached at opposite ends to trays 224 and 230.

In the illustrated embodiment, a portion of cleaned air 14D is ejected from exhaust hood 200 as pressurized air 14E. This pressurized air 14E may be ejected from exhaust hood 200 from a number of separately located orifices. The ejected pressurized air 14E may comprise the characteristics of, and achieve the various desired outcomes described in relation to air curtains 20, 40 and 50 in the FIG. 1 embodiment for exhaust hood 10. Concurrently, a portion of clean air 14D is ejected from housing 200 as recirculated air 14F at a lower pressure as compared to that of pressurized air 14E.

As best shown in FIG. 6, cleaned air 14D which passes through fans 222A and 222B may travel through openings 244A and 244B located on opposing side walls of housing 210 (collectively referred to herein as openings 244) as pressurized air 14E. Openings 244A and 244B respectively permit pressurized air 14E to flow into side plenums 242A and 242B (collectively referred to herein as side plenums 242). As best shown in FIG. 5, exhaust hood 200 comprises an opening 236 defined in housing 210. In the illustrated embodiment, cleaned air 14D which passes through filter 228 exits into the surrounding kitchen environment as recirculated air 14F through opening 236. In other embodiments, opening 236 connects to a duct system of the building for expelling cleaned air 14F into the external atmosphere.

FIG. 7 is a low-angle perspective view of exhaust hood 200. FIG. 7 shows a lower plenum 246 that is in fluid communication with side plenums 242. Lower plenum 246 extends around the sides and front of hood 200 at a bottom portion of hood 200. Lower plenum 246 comprises a forward-facing angled edge 254. Edge 254 comprises a plurality of orifices 256 through which pressurized air 14E is ejected to create an air curtain according to the principle described above in relation to air curtain 20. Lower plenum 246 additionally comprises a rearward facing surface 258. Surface 258 comprises a plurality of orifices 260 through which pressurized air 14E is ejected to create an air curtain according to the principle described above in relation to air curtain 40. Lastly, lower plenum 246 comprises downward facing surfaces 262 at opposed bottom side edges of hood 200. Surface 262 comprises a plurality of orifices 264 through which pressurized air 14E is ejected to create an air curtain according to the principle described above in relation to air curtain 50. In the illustrated embodiment, lower plenum 246 extends downward from hood 200 to form a recessed canopy 237.

FIG. 8 is a side-elevation view of exhaust hood 200 whereby side plenum 242A is omitted to show opening 244A. As illustrated, openings 244 comprise an H-shaped opening, although other shapes of openings are possible. In some embodiments, the size of openings 244 are dynamically configurable to achieve a desired pressure within side plenums 242 and to adjust the velocity of air 14E exiting orifices 254, 260 and 264. In some embodiments, openings 244 are dynamically configurable by way of one or more flexible bendable flaps which can be positioned to selectively obstruct cleaned air 14D from entering portions of openings 244. By increasing the unobstructed area of openings 244, the velocity of air curtains generated by exhaust hood 200 is increased. Conversely, an increase in the obstructed area of openings 244 results in the generation of lower velocity air curtains by hood 200.

FIG. 9 is a detailed perspective view of exhaust hood 200 showing lower plenum 246 having an exterior side surface omitted to illustrate baffle 250B disposed within the interior of lower plenum 246. As shown in FIG. 8, a baffle 250A may be provided on the opposite side of exhaust hood 200. It will be appreciated that the features described in relation to baffle 250B are equally applicable to baffle 250A, and vice versa. Baffles 250 may be coupled to housing 210, lower plenum 246, or both in any appropriate manner. As shown in FIG. 6, baffles 250 comprise an angled bracket that is secured to lower plenum 246 by way of a bolted connection. Returning to FIG. 9, baffle 250B comprises a plurality of elongated perforations 252, only a number of which are indicated.

As pressurized air 14E exits side plenums 242, baffles 250 have the effect of impeding the flow of air 14E to edges 262. In this manner, a greater volume of air 14E is permitted to flow to the front of lower plenum 246, where orifices 256 and 260 are located, compared to if baffles 250 were absent. A suitable number and length of perorations 252 are provided on baffles 250 to increase the volume of air 14E reaching orifices 264 so as to achieve a desired velocity and velocity profile of air exiting orifices 264. In some embodiments, an angle of baffles 250 relative to lower plenum 246 is configurable to achieve a desired distribution of pressurized air 14E along different portions of lower plenum 246.

Exhaust hood 200 comprises a number of features for connecting powered components within hood 200 to a power source. As best shown in FIG. 6, exhaust hood 200 comprises a junction box 248 for enclosing and protecting electrical components and connections. Junction box 248 comprises a suitable connector interface for receiving power from a power source in the surrounding kitchen environment. Junction box 248 further comprises suitable interfaces for delivering power through one or more power cables to each of fans 222A and 222B. As best shown in FIG. 7, exhaust hood 200 comprises a switch 266. Switch 266 may be operated by a user to control an ON/OFF operational state of fans 222, light 268, or both. Exhaust hood additionally comprises a control knob 270 which may be operated by a user to control a power setting of fans 222. Control knob 270 may comprise electrical components such as a potentiometer, a variable capacitor, a rotary switch, and the like.

Preferably, the interior of housing 210 of exhaust hood 200 is easily accessible during the lifecycle of exhaust hood 200 for servicing or replacing filters 214, 218 and 228 and fans 222. FIG. 8 shows a number of doors 272A, 272B and 272C (collectively referred to herein as doors 272) which may each permit access to a portion of the interior of housing 210. Access to the interior of housing 210 may be conferred by doors 272 by any appropriate means. For example, doors 272 may be slideable, pivotable or detachable to expose a particular interior part of exhaust hood 200.

One aspect of the present invention provides a method for controlling the operation of an exhaust hood that provides one or more air curtains to create a region of negative pressure which draws effluent plumes toward the exhaust hood. With reference to exhaust hood 10 of the FIG. 1 embodiment, some embodiments of the present invention provide a series of manual controls which control operating parameters for one or more of:

-   -   a flow rate and/or velocity (which may be zero) of angled air         curtain 20;     -   a flow rate and/or velocity (which may be zero) of rearward         facing air curtain 40;     -   a flow rate and/or velocity (which may be zero) of side air         curtains 50;     -   an angle θ of air curtains 20 and/or 50;     -   a suction power (which may be measured in cubic feet per minute)         of one or more fans within exhaust fan assembly 18; and     -   a suction power (which may be zero) of intake fan 32.

Manual control of the above operating parameters of exhaust hood 10 may be embodied in an interface whereby several options (such as LOW, MEDIUM, or HIGH) are made selectable to a user. Selection of one of these options may change a plurality of these operating parameters to preset levels.

In some embodiments, control of one or more of the above operating parameters is performed automatically. FIG. 10 shows a system 300 comprising an exhaust hood 10 as described herein. System 300 comprises a sensing subsystem 310 which comprises heat sensor 312, appliance state sensor 314 and particulate matter sensor 316. Controller 320 provides overall control over the operation of system 300. Controller 320 is operable to receive signals from sensing subsystem 310 and to appropriately automatically adjust operating parameters of exhaust hood 10. Use of other sensors and combinations of sensors are possible in providing sensing subsystem 310.

For example, heat sensor 312, located in or around exhaust hood 10, detects hot air created by a cooking event and which rises through convection. If controller 320 determines that the temperature sensed by heat sensor 312 exceeds a setpoint temperature, indicating that cooking activity is occurring, controller 320 may cause exhaust hood 10 to turn on. Appliance state sensor 314 may detect an electric current or the presence of gas, which indicates operation of the cooking appliance. Controller 320 may use this signal to automatically operate exhaust hood 10. Operation of exhaust hood 10 based on the appliance state can optionally consider the operating parameters of the cooking appliance (e.g. the heat setting of one or more heating elements) to appropriately control the parameters of exhaust hood 10.

Particulate matter sensor 316 may detect the concentration of particulate matter in any rising cooking effluent plumes, the level of which may be used by controller 320 to appropriately control exhaust hood 10. In some embodiments, particulate matter sensor 316 comprises an optical laser-based sensor to detect particulate matter concentration. Upon detection of a particulate matter concentration exceeding a setpoint value, controller 320 may turn on one or more exhaust fans within exhaust hood 10. In some embodiments, the strength of one or more fans of exhaust hood 10 may be operated at a number of settings based on the concentration of detected particulate matter, with stronger concentrations resulting in a stronger fan setting.

In some embodiments, automatic control of exhaust hood 10 by controller 320 comprises adjusting operating parameters to achieve a flow rate and/or velocity of air curtains 20, 40 and 50 at levels which are appropriate for the sensed level of cooking activity (detected by one or more of sensors 312, 314 and 316). For example, controller 320 may select an operating level for exhaust fan assembly 18 of exhaust hood 10 which creates minimal noise while being effective to draw a majority of plumes 14 into exhaust hood 10.

In some embodiments, multiple heat sensors 312, appliance state sensor 314 and/or multiple particulate matter sensors 316 may be provided to determine the source of cooking activity on cooktop 12. Such information may be used by controller 320 for automatic control of an adjustable angle θ of air curtain 20 and/or air curtain 50. For example, if effluent plumes 14 originate only from cooking activity at the rear of cooktop 12 proximate to wall 11, controller 320 may adjust air curtain 20 to be ejected at a lower angle (i.e. smaller θ) so as to avoid causing unnecessary discomfort to an individual cooking under exhaust hood 10. The angle of air curtain 20 may be modified, for example, by way of adjusting the angle of one or more nozzles through which air curtain 20 is generated.

FIGS. 11A and 11B depict computational fluid dynamic (CFD) simulations of the effect of air curtains 20 and 40 on gas flow velocity profiles in the operation of exhaust hood 10. The velocity field of effluent plumes 14 created by cooking activity is depicted by arrows whose length and density are representative of plume 14′s velocity and density and that of any air curtains generated by exhaust hood 10.

FIG. 11A depicts a CFD simulation wherein exhaust hood 10 does not generate air curtains 20 and 40. As illustrated, a portion of plumes 14G escapes from the front of hood 10 into the surrounding kitchen environment. Further, a turbulent eddy 14H forms at a front of exhaust hood 10 which may cause oil and pollutant deposits to form on the bottom of exhaust hood 10. Accordingly, a certain portion of plumes 14 is not captured by vents 16 in the FIG. 11A simulation.

FIG. 11B depicts a CFD simulation wherein exhaust hood 10 generates air curtains 20 and 40. As illustrated, plumes 14 do not escape the front of exhaust hood 10 due in part to the region of negative pressure created by the generation of air curtain 20. Furthermore, the FIG. 11B simulation illustrates that an efficient airflow of plumes 14 across the bottom of hood 10 and into vents 16 is encouraged by the generation of air curtain 40.

FIG. 12A depicts a CFD simulation wherein exhaust hood 10-1 generates a substantially vertical air curtain 20-1 from a horizontal edge 22-1. FIG. 12B depicts a CFD simulation wherein exhaust hood 10-2 generates an air curtain 20-2 at an angle θ from an angled edge 22-2 (similar to edge 22 illustrated in the FIG. 1 embodiment). Both of the FIGS. 12A and 12B simulations depict scenarios where plumes 14 originate from cooking activity in a portion of cooktop 12 in front of exhaust hoods 10-1 and 10-2 (to the right in the illustrated simulations).

The FIGS. 12A and 12B CFD simulations illustrate that a smaller quantity of plumes 14G escape from the front of hood 10 into the surrounding kitchen environment when an angled air curtain 20-2 (FIG. 12B) is generated as compared to a vertical air curtain 20-1 (FIG. 12A). Furthermore, the area to the right of edge 22-2 on the front surface of exhaust hood 10-2 in the FIG. 12B angled configuration shows nearly no gas flow as compared to the same area to the right of edge 22-1 in the FIG. 12A configuration. This illustrates the increased effectiveness of the angled FIG. 12B configuration in drawing plumes 14 toward the region of low pressure around edge 22-2.

FIGS. 13A and 13B depict simulations of a plume of steam originating from a forwardly located cooking surface, the steam being drawn into vents of exhaust hoods 10-1 and 10-2, respectively. As shown in the FIG. 13A configuration comprising an exhaust hood 10-1 which generates a vertical air curtain, a portion of steam escapes along the front surface of exhaust hood 10-1, indicated by 14G. Conversely, no escape of steam is shown in the FIG. 13B configuration comprising an exhaust hood 10-2 which generates an angled air curtain (similar to that shown in FIG. 12B). Without wishing to be bound by theory, it is believed by the inventors that the provision of an angled air curtain is beneficial to improving capture efficiency in exhaust hood configurations where a cooking surface beneath the hood extends farther from a wall than the exhaust hood.

Interpretation of Terms

Unless the context clearly requires otherwise, throughout the description and the claims:

-   -   “comprise”, “comprising”, and the like are to be construed in an         inclusive sense, as opposed to an exclusive or exhaustive sense;         that is to say, in the sense of “including, but not limited to”;     -   “connected”, “coupled”, or any variant thereof, means any         connection or coupling, either direct or indirect, between two         or more elements; the coupling or connection between the         elements can be physical, logical, or a combination thereof;     -   “herein”, “above”, “below”, and words of similar import, when         used to describe this specification, shall refer to this         specification as a whole, and not to any particular portions of         this specification;     -   “or”, in reference to a list of two or more items, covers all of         the following interpretations of the word: any of the items in         the list, all of the items in the list, and any combination of         the items in the list;     -   the singular forms “a”, “an”, and “the” also include the meaning         of any appropriate plural forms.

This description employs a number of simplifying directional conventions. Directions are described in relation to a kitchen having an existing vertical wall and an existing cooktop. Directions may be referred to as “rear”, “rearward”, “back”, or the like if they tend toward the vertical wall; “front”, “forward”, or the like if they tend opposite the vertical wall; “upward”, “above”, “higher”, or the like if they tend away from the cooktop; “below”, “lower”, “down”, “downward”, or the like if they tend toward the cooktop; “horizontal”, “side”, or the like if they tend in a direction orthogonal to the vertical direction. Those skilled in the art will appreciate that these directional conventions are used for the purpose of facilitating the description and should not be interpreted in a narrow literal sense.

For example, while processes or blocks are presented in a given order, alternative examples may perform routines having steps, or employ systems having blocks, in a different order, and some processes or blocks may be deleted, moved, added, subdivided, combined, and/or modified to provide alternative or subcombinations. Each of these processes or blocks may be implemented in a variety of different ways. Also, while processes or blocks are at times shown as being performed in series, these processes or blocks may instead be performed in parallel, or may be performed at different times.

In addition, while elements are at times shown as being performed sequentially, they may instead be performed simultaneously or in different sequences. It is therefore intended that the following claims are interpreted to include all such variations as are within their intended scope.

Specific examples of systems, methods and apparatus have been described herein for purposes of illustration. These are only examples. The technology provided herein can be applied to systems other than the example systems described above. Many alterations, modifications, additions, omissions, and permutations are possible within the practice of this invention. This invention includes variations on described embodiments that would be apparent to the skilled addressee, including variations obtained by: replacing features, elements and/or acts with equivalent features, elements and/or acts; mixing and matching of features, elements and/or acts from different embodiments; combining features, elements and/or acts from embodiments as described herein with features, elements and/or acts of other technology; and/or omitting combining features, elements and/or acts from described embodiments.

Various features are described herein as being present in “some embodiments”. Such features are not mandatory and may not be present in all embodiments. Embodiments of the invention may include zero, any one or any combination of two or more of such features. This is limited only to the extent that certain ones of such features are incompatible with other ones of such features in the sense that it would be impossible for a person of ordinary skill in the art to construct a practical embodiment that combines such incompatible features. Consequently, the description that “some embodiments” possess feature A and “some embodiments” possess feature B should be interpreted as an express indication that the inventors also contemplate embodiments which combine features A and B (unless the description states otherwise or features A and B are fundamentally incompatible).

It is therefore intended that the following appended claims and claims hereafter introduced are interpreted to include all such modifications, permutations, additions, omissions, and sub-combinations as may reasonably be inferred. The scope of the claims should not be limited by the preferred embodiments set forth in the examples, but should be given the broadest interpretation consistent with the description as a whole. 

1. An exhaust hood for capturing effluent plumes produced by cooking activity, the exhaust hood comprising: at least one fan operable to create a region of negative pressure beneath the exhaust hood for drawing air entraining the effluent plumes into the exhaust hood; one or more plenum chambers in fluid communication with the exhaust fan; one or more first orifices in fluid communication with the one or more plenum chambers, the first orifices located along a front edge of the exhaust hood; and a filter for cleaning the air drawn into the exhaust hood, wherein, by action of the exhaust fan drawing the air entraining the effluent plumes into the exhaust hood, the air is drawn through the filter to yield cleaned air; wherein at least a portion of the cleaned air that has been pressurized by the fan is delivered into the one or more plenum chambers and wherein the first orifices are configured to eject the portion of the cleaned air as one or more first jets arranged to provide a first air curtain.
 2. The exhaust hood according to claim 1 comprising one or more second orifices in fluid communication with the one or more plenum chambers and configured to eject at least a portion of the cleaned air in a rearward direction as one or more second jets.
 3. The exhaust hood according to claim 2 wherein the second jets are oriented generally horizontally.
 4. The exhaust hood according to claim 2 comprising one or more third orifices in fluid communication with the one or more plenum chambers and configured to eject at least a portion of the cleaned air in a downward direction as one or more third jets to provide at least one second air curtain extending along at least one side of the exhaust hood.
 5. The exhaust hood according to claim 4 comprising one or more baffles disposed in the one or more plenum chambers, the one or more baffles adjustable to vary a distribution of the cleaned air between the first orifices and the third orifices.
 6. The exhaust hood according to claim 1 wherein the first orifices are positioned on a forward-facing surface of the exhaust hood.
 7. The exhaust hood according to claim 6 wherein a forward edge of exhaust hood is spaced by 12 inches from a rear of the exhaust hood that is designed to be against a wall.
 8. The exhaust hood according to claim 1 wherein the exhaust hood is mounted over a cooktop, the cooktop comprising an area which extends past a front portion of the exhaust hood, and wherein the orifices are oriented to direct the first jets at a forward angle θ.
 9. The exhaust hood according to claim 8 wherein the forward angle θ is such that the first air curtain is angled to slightly clear the outer edge of the cooktop.
 10. The exhaust hood according to claim 8 wherein the first air curtain has an angle of 28 degrees ±2 degrees from vertical.
 11. The exhaust hood according to claim 1 wherein an angle of the first air curtain is adjustable.
 12. The exhaust hood according to claim 1 comprising a generally horizontal diffuser supported at a lower portion of the exhaust hood behind the first air curtain, the diffuser configured to block upward motion of effluent plumes and to concentrate the region of negative pressure around a perimeter of the exhaust hood.
 13. The exhaust hood according to claim 1 wherein an overall length of the exhaust hood is smaller than an overall length of a cooking appliance over which the exhaust hood is configured to be mounted.
 14. The exhaust hood according to claim 1 comprising panels that extend downwardly around a bottom perimeter of the exhaust hood to form a recess on a bottom side of the exhaust hood.
 15. The exhaust hood according to claim 1 wherein the filter is an activated carbon filter.
 16. The exhaust hood according to claim 1 wherein the at least one fan comprises comprising a second fan located downstream of the filter, the second fan operable to pressurize the one or more plenum chambers with the cleaned air.
 17. The exhaust hood according to claim 1 further comprising an intake fan operable to draw ambient air into the one or more plenum chambers.
 18. The exhaust hood according to claim 1 comprising a controller configured to control one or more of: a flow of the cleaned air that is directed to the first air curtain; and an angle of the one or more first jets.
 19. An exhaust hood for capturing effluent plumes produced at a cooktop, the exhaust hood comprising: a body mountable against a wall, the body having a rear side for abutting the wall and a front side spaced from the rear side, the body having vents formed on a lower surface thereof; a fan within the body and toward the rear side of the body, the fan connected to draw air and any entrained cooking effluent through the vents into an interior space of the exhaust hood and to deliver at least some of the air through a filter and into a plenum located within the exhaust hood; first apertures arranged along the front side of the body, the apertures fluidly coupled to the plenum and arranged to provide a first air curtain that extends across the front side of the body and is directed forward and downward from the exhaust hood.
 20. The exhaust hood according to claim 19 wherein the front and rear surfaces of the body are spaced apart by a distance of about 12 inches, the exhaust hood includes second apertures arranged to extend along one or two lateral sides of the exhaust hood between the front and rear sides of the body, the second apertures fluidly coupled to receive filtered pressurized air within the body to provide a second air curtain that extends along one or both of the lateral sides of the body and is directed downwardly from the exhaust hood. 